Biology subjects

Rueger, L.

Publications and source records attributed to Rueger, L..

3 recordsLinked to original sources

bioRxiv2026

A membrane-anchored inhibitor of papain-like cysteine proteases promotes Pseudomonas root colonization

Pseudomonas species, spanning both beneficial and pathogenic lifestyles, possess conserved mechanisms to modulate plant immunity. Nevertheless, the mechanisms by which commensal bacteria establish and maintain host colonization remain poorly understood. Here, we report the characterization of a Pseudomonas chagasin-like protease inhibitor (Cpi1), conserved across pseudomonads representing a novel class of membrane-anchored PLCP inhibitor. Unlike previously described secreted protease inhibitors, P. putida Cpi1 is a lipoprotein localized to the bacterial surface and outer membrane vesicles (OMVs), positioning it to selectively inhibit immune-related papain-like cysteine proteases (PLCPs) during host interactions. Functional assays demonstrated inhibition of maize PLCP activity in the nanomolar range, while cpi1 deletion and chagasin motif mutants exhibited significantly impaired early root colonization, particularly in the meristematic and elongation zones. Besides, lack of cpi1 resulted in an altered structure of a maize root-associated synthetic community. We hypothesize that, Cpi1 may protect critical bacterial surface proteins from cleavage by inhibiting plant proteases and thereby modulate the release of MAMPs, dampening host immune responses. Moreover, the release of Cpi1 via OMVs could further extend its function within the root periphery and the apoplast. Together, our results uncover a conserved, membrane-anchored mechanism among pseudomonads for subverting plant immunity and establishing host-microbe interactions.

microbiology↗

bioRxiv2026

Transport-driven spatial patterning of glucosinolates structures root microbiome assembly

Plant roots actively assemble distinct microbial communities, yet how host chemical traits are organized to structure them remains poorly understood. Glucosinolates are hallmark defense metabolites of Brassicaceae, but their axial distribution in roots and ecological relevance belowground remain largely unknown. Here, we combine spatial metabolite profiling and microbiome analysis in Arabidopsis thaliana and the oilseed crop Camelina sativa using mutants lacking the glucosinolate transporters GTR1 and GTR2. We find that both species exhibit a conserved, transporter-dependent enrichment of long-chained aliphatic glucosinolates at the root tip, revealing active axial organization of chemical defenses in roots. Using 16S rRNA amplicon-based sequencing, we show that plant species identity is the primary determinant of bacterial community composition. However, disruption of axial glucosinolate distribution significantly alters spatial patterns of microbiome assembly along the root in a species-dependent manner. In Arabidopsis, this assembly effect is most pronounced in the rhizosphere, whereas in Camelina, root-associated communities were also affected. Together, our findings demonstrate that glucosinolate transport establishes chemical landscapes along the root axis, thereby shaping spatial patterns of microbiome assembly. This identifies spatially structured specialized metabolite allocation as an important mechanism by which plants shape their belowground microbial environment.

plant biology↗

bioRxiv2024

Microbial utilisation of maize rhizodeposits applied to an agricultural soil at a range of concentrations

Rhizodeposition fuels carbon (C) and nutrient cycling in soil. However, the dynamics of microbial growth on rhizodeposits in relation to the distance from the root have not been well studied. This study investigates microbial growth on individual organic components of rhizodeposits and on maize root-derived exudates and mucilage from an agricultural soil. By creating a gradient of substrate concentrations, we simulated reduced microbial access to rhizosphere C with increasing distance to the root surface. We identified distinct C-thresholds for the activation of microbial growth, and these were significantly higher for rhizodeposits compared to singular, simple sugars. In addition, testing for stoichiometric constraints of microbial growth by supplementing N and P showed accelerated and increased microbial growth by activating a larger proportion of the microbial biomass. Early and late season exudates triggered significantly different microbial growth responses. The mineralisation of early season exudates was induced at a high C-threshold, whereas the mineralisation of late season exudates showed sugar-like properties, with a low C-threshold, high substrate affinity, and a reduced maximum respiration rate. Mucilage exhibited the highest C-threshold for the activation of microbial growth, although with a short lag-period and with an efficient mucilage degradation comparable to that of sugars. By determining kinetic parameters and turnover times for different root-derived substrates, our data enable the upscaling of micro-scale processes to the whole root system, allowing more precise predictions of how rhizodeposits drive microbial C and nutrient dynamics in soil. HighlightsO_LIGrowth thresholds for rhizodeposits were significantly higher than for singular, simple sugars. C_LIO_LINo distinct microbial growth on root exudates was observed even at high concentrations. C_LIO_LIMucilage has a short lag-phase and efficient decomposition like sugars but only above a high threshold. C_LIO_LIN and P limited microbial growth in the agricultural soil. C_LI

ecology↗